1. Field of the Invention
The invention relates in general to filters for use in power systems and in particular to a filter for removing harmonic current from a neutral conductor in a multiple phase power system.
2. Prior Art
Nonlinear loads on a power distribution system can draw a high level of harmonic current from the power source. In particular, low-cost rectifier loads, as commonly used in personal computers and associated hardware, draw a load current is very rich in triplen (3,9, . . . ) harmonics, with the third harmonic being predominant. At the three-phase source, this third harmonic content of load current is mostly of a zero-sequence nature. The consequence is that the neutral conductor in a 4-wire, 3-phase supply system is heavily loaded with third harmonic current. This creates a need to overrate the neutral conductor and the main supply transformer.